Bladder catheters are routinely used for draining the urinary tract of patients who are unable to voluntarily urinate and in whom the accurate measurement of urine production is necessary. Commonly used bladder catheters have a number of problems associated with them. First, they do not completely drain the bladder because urine will collect in a dependent portion of the bladder, away from apertures in the distal catheter. This residual urine, in conjunction with the artificial passage created by the catheter, tends to produce urinary tract infections. These infections occur within hours to days after the initiation of continuous bladder drainage.
Further, measuring changes in urine output is critical to determining the cardiovascular and renal status of severely ill patients. Many of these patients are hospitalized in intensive care units and convalesce while supine. The supine position promotes collection of residual amount of urine in dependent portions of the bladder away from the opening of commonly used bladder catheters. In such patients, intermittent movement causes the residual amounts of urine to unpredictably contact the drainage opening of the catheter. This gives the impression that a large amount of urine was produced since the last measurement followed by substantially decreased production of urine as the urinary output flows again to the dependent portion of the bladder. Similarly, patients on rotating beds for the prevention and treatment of bed sores, such as with quadriplegics, will also appear to have irregular production of urine due to the unpredictable movement of significant amounts of urine to the catheter opening as the bed rotates. Thus, the accurate measurement of urine output is difficult with commonly used bladder catheters.
A number of bladder catheters have been developed that attempt to drain residual amounts of urine. Some of these have a drainage opening at the junction of the bladder and urethra. While some of these designs will drain urine when the junction is also the most dependent portion of the bladder, they do not drain residual urine from the dependent portions of the bladder away from the junction such as when the patient is horizontal. Thus, there remains a need for a bladder catheter that will continuously drain urine from the dependent portions of a bladder when the patient is supine.